LDPC concatenation rules for IEEE 802.11n system with packets length specified in octets

Abstract

An improved LDPC encoding with concatenation rule and code size with packet lengths specified in octets is provided. The LDPC block size is selected to be an integer number of OFDM tones. The concatenation rule is an improvement of the shortening and puncturing scheme for low data rate. The improvement is two fold. First, the code length is selected based on the number of transmitted information bits in octets (HTLENGTH). Second, it is determined whether one extra OFDM symbol padding should be added based on the number of shortening bits in the last codeword and the available padding bits in the last OFDM symbol.

Description

FIELD OF THE INVENTION [0001] The present invention related to wireless systems, and in particular, to structured Low Density Parity Check codes for wireless systems. BACKGROUND OF THE INVENTION [0002] Low Density Parity Check (LDPC) codes have recently attracted considerable attention owing to their capacity-approaching performance and low complexity iterative decoding. LDPC codes can be applied to a wide range of applications such as wireless communications, satellite communications and storage. [0003] Currently, LDPC code is considered for in the high throughput wireless local area networks (WLAN), such as IEEE 802.11n, as an optional advanced code to improve system throughput. However, several issues need to be solved to match the LDPC code with unique system characteristics of different WLAN systems. First is the code size. Since LDPC code works better with longer code size, the code size should be selected as large as possible to ensure performance. However, since a WLAN syste...

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Benefits of technology

[0008] Accordingly, the present invention provides a simpler LDPC encoding approach wherein encoding parameters are determined using simple calculation without exhaustive search. The encoding according to the present invention is further more efficient than the WWiSE and TGn Sync approaches, and provides improved coding performance for very short packet compared with the current TGn Sync approach.

Problems solved by technology

However, several issues need to be solved to match the LDPC code with unique system characteristics of different WLAN systems.

However, since a WLAN system is a random access based system, the code size is limited by the SIFS (Short Inter-Frame Space) decoding budget.

Second, in high-throughput WLAN systems, the transmitted PPDU (Physical Protocol Data Unit) is large, which requires using several LDPC codewords.

A method for concatenating the LDPC codeword within a PPDU is an important design issue.

This approach provides the simplest solution, but the worst performance in terms of extra OFDM padding efficiency.

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